Rotary switch detent spring



1959 K. c. ALLISON ETAL RO'II'ARY SWITCH DETENT SPRING Filed Sept. 27, 1955 INVENTQRS.

p 2,869,395 ROTARY SWITCH DETENT SPRING Kenneth C. Allison, Crystal Lake, and William L. Hoehn,

' Chicago, Ill.

Application September 27, 1955, Serial No. 536,959

9 Claims. (Cl. 74-527) This invention relates to an index mechanism of the type used in radio and television rotary switch installations wherein detents on a mounting plate in which the switch operating shaft is journalled have selective engagement with a riding point on an index spring plate fixed to the shaft so as to control the rotation of the shaft into several indexed positions.

An object of this invention is to provide such'an index mechanism embodying an indexing spring plate wherein the riding point is at an abruptly shorter radial distance from the shaft than the'portions of the arms joiningsaid riding point to the hub of the spring plate. By thus shortening the distance of the riding point from the axis of rotation, the length of the path of the point is reduced to thereby reduce wear of the point. At the same time, the inwardly offset arrangement of the riding point adds length to the arms which join the point to the hub so as to avoid fatigue failure in the spring plate.

With these and other objects in view, reference is had to the accompanying drawings, wherein:

Fig. 1 is a fragmentary plan view of a switch mounting plate and showing the index plate embodying this invention in association with a switch operating shaft journalled in said mounting plate.

Fig. 2 is an edge view of the assembly shown in Fig. 1 with parts in section, as said assembly appears when viewed from the top of Fig. 1.

Fig. 3 is a section taken on line 33 of Fig. l, with parts in elevation.

Reference being had more particularly to the drawings, a spring index plate designated generally by the numeral and more particularly described hereinafter, is shown as fixed to an operating shaft 11 mounted for rotation in a bushing 12 carried by a mounting plate or index base 13.

The portion of the shaft 10 extending inwardly from the bushing 12 has opposite portions removed to provide flattened sides 14 and 15 so as to have keyed connection with the rotary members of switch sections (not shown) to be operated by said shaft. The inner edge of the bushing 12 engages a C-washer 16 fitted in a groove 17 formed in the shaft 11 whereby axial movement of the shaft in the direction of the mounting plate 13 is limited except when the G-washer is removed. 7

Flattened sides are also provided on the portion of the shaft 10 extending outwardly from the mounting plate which form continuations of the flattened sides 14 and 15 whereby the spring index plate 10 has keyed connection to said portion of the shaft on the outside of the mounting plate. The plate 10 is also fastened against a shoulder formed in the shaft 11 by means of staking ears formed integrally with the shaft 11.

As shown in Fig. 1, the spring index plate 10 includes a pair of arms 19 and 20 projecting in opposite directions from a hub portion 18. A slot 21 which extends circumferentially of the shaft 11 through an arc of approximately 180 degrees is defined by the inner edge of segments 22 and 23 forming extensions of the arms 19 and 20, respectively, joined by an integral bridge portion 24, and

"ice

the inner edges of the hub portion 18 and the inner edges of the arms 19 and 20 which form continuations of said inner edges of the segments 22 and 23. Thus the arms 19 and 20 are adapted to flex relative to the hub portion it; along a line extending diametrically through the shaf The segments 22 and 23 have a convexly curved outer edge and the bridge portion 24 connecting said segments :22 and 23 presents an outer edge portion at anabruptly shorter radial distance from the shaft than the outer edge of said segments 22 and 23. The bridge portion 24 and the abruptly inturned ends of the segments 22 and 23 through which the latter are joined to the bridge portion 24 affords a prolongation of the arms 19 and 20 which is of sufficient added length to better counteract forces which produce fatigue failure in the spring blade.

A series of openings 25 formed in the mounting plate 13 in the path of the bridge portion 24 are selectively engageable with a detent or projection 26 extending from the face of the bridge portion 24 facing the mounting plate 13. It will be noted that the bridge portion 24 is offset axially toward the mounting plate 13 in relation to the plane of the hub portion 18 of the index spring 10 and :that the pressure applied against the shaft 10 by the: pressure of the bridge portion 24 against the mounting plate acts to retain the C-washer in engagement with the bushing 11.

It will also be noted that the edges of the segments 22 and 23 defined by the slot 21 are arranged on a curvature at progressively increasing distances from the shaft in a direction toward the bridge portion 24 whereby said segments are of gradually reduced width in a direction away from the line of fiexure of the arms of the hub portion 18. That edge of each of the segments 22 and 23 so defined by the slot 21 and which is most distant from the shaft 11 is thus located at a greater distance from the shaft 11 than both the inner and the outer edges of the bridge section 24. Such lengthening of the segments 22 and 23 in relation to the bridge section 24 is effective to supply increased resistance to fatigue failure in the spring plate 10.

As shown in Fig. 1, the detent is arranged along the inner edge of the bridge portion 24 which is located at a radial distance from the shaft less than the shortest radial distance between the shaft 11 and the nearest edge portion of the segments 22 and 23. Such reduction of the distance between the riding point 26 of the plate 10 and the shaft 11 is effective to shorten the length of the are which the point 26 travels during indexing operations whereby wear of said riding point on the mounting plate 1.3 is accordingly reduced.

What is claimed is:

1. An indexing mechanism for switches comprising a mounting plate having a shaft journalled therein, a plurality of indexing means formed in said plate circularly of said shaft, an index spring formed of flat spring stock to provide a hub portion through which said index spring is fixed to said shaft, a pair of arms projecting in opposite directions from said hub portion, a slot extending circumferentially of said shaft through an arc of approximately degrees defined by the edge portions of segments forming continuations of said arms, and the edge portion of a bridge section connecting the ends of said segments remote from said arms, and the inner edge portions of the hub portions and said arms facing said segments and forming continuations of said edge portions of said segments, each of said segments presenting a convexly curved outer edge portion, said bridge section having its outer edge portion at an abruptly shorter radial distance from the shaft than the outer edge of said segments and being offset axially from the plane of the hub portion, and means on said bridge section engageable with said indexn t .a d o set xially m he plan ott r d portion in the direction said bridge portion is offset axially from the plane of the htib portion.

2. Ar indexingmechanism as defined in claim 1 where- ;in the outer edge of said segrnents is arranged on the arc of a circle concentric With the axis of rotation of the shaft.

3. An indexing mechanism-as defined in claim 1 wherek in the edge of each segment defining said slot is arranged on a curvature at progressively increasing distances from the shaft in a direction toward said bridge section.

4. An indexing mechanism as defined in claim 1 wherein the outer edge of the bridge section'is at a shorter radial distance from the shaft than the inner edge of the segments 'inost distant from said shaft.

:5. An indexing mechanism as defined in claim 1 wherein the edge of each segment defining said slot is arranged on a-curvatu're at progressively increasing distances from the shaft in a direction toward said bridge section and the outeredge of the'bridge section is at a shorter radial distance from the shaft than portions of said latter edge of the segments most distant from said shaft.

6. An indexing mechanism as defined in claim 1 Wherein the edge of each segment defining said slot is arranged on a curvature at progressively increasing distances from the shaft in a direction toward said bridge section and the inner edge of the bridge section is at a radial distance from theshaft less than the distance between the shaft and portions of said latter edge of the segments nearest saidshaft.

-7- An i ex n mech nis n. as. cfinett n. l im .L thsisin the edge of each segment defining said slot is arranged on a curvature at progressively increasing distances from the shaft in a direction toward said bridge section, the inner edge of the bridge portion is at a radial distance from the shaft less than the distance between the shaft and portions of said latter 'edge of the segments nearest said shaft, and said means on the bridge section engageable with said-indexingmeans are-" arranged"-a'long the aforesaid inneredge of said bridge portion.

8. An indexing mechanism as-dfiried in cla'irn l wherein said means on the bridge' portion engageable with said indexing -means comprises an integral "outwardly formed inner edge area of said bridge portion.

9. An indexing 'rnechanis'm asde'finedin claim 1 wherein the outer edge of said segments is arranged on the arc of a circle concentric with the axis of rotation of the shaft and the edge of each blade segment defining said slot is arranged on a curvature atfpro'gressivelyincreasing distances from the shaft in'a'direc'tion toward said bridge section.

References Cited in the file of this patent UNITED STATES PATENTS 2,115,245 Allison Apr. 26, 1938 2,115,284 Pratt Apr/26, 1938 2,130,219 Allison et al Sept. 13, 1938 2,292,717 Rubenstein Augj'l l, 1942 

